From b2d50392eab891a177447225d69a46e97d30a5e8 Mon Sep 17 00:00:00 2001
From: Michael-F-Bryan <michaelfbryan@gmail.com>
Date: Wed, 27 May 2020 02:23:36 +0800
Subject: [PATCH] Emit redirects towards the end of the rendering process

---
 src/config.rs                                |  1 +
 src/renderer/html_handlebars/hbs_renderer.rs | 48 +++++++++++++++++++-
 src/theme/mod.rs                             |  6 +++
 src/theme/redirect.hbs                       | 12 +++++
 4 files changed, 66 insertions(+), 1 deletion(-)
 create mode 100644 src/theme/redirect.hbs

diff --git a/src/config.rs b/src/config.rs
index 15c041cb..71edbaf2 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -539,6 +539,7 @@ impl Default for HtmlConfig {
             git_repository_url: None,
             git_repository_icon: None,
             livereload_url: None,
+            redirect: HashMap::new(),
         }
     }
 }
diff --git a/src/renderer/html_handlebars/hbs_renderer.rs b/src/renderer/html_handlebars/hbs_renderer.rs
index d58bc805..2953f098 100644
--- a/src/renderer/html_handlebars/hbs_renderer.rs
+++ b/src/renderer/html_handlebars/hbs_renderer.rs
@@ -9,7 +9,7 @@ use crate::utils;
 use std::borrow::Cow;
 use std::collections::BTreeMap;
 use std::collections::HashMap;
-use std::fs;
+use std::fs::{self, File};
 use std::path::{Path, PathBuf};
 
 use handlebars::Handlebars;
@@ -279,6 +279,46 @@ impl HtmlHandlebars {
 
         Ok(())
     }
+
+    fn emit_redirects(
+        &self,
+        root: &Path,
+        handlebars: &Handlebars<'_>,
+        redirects: &HashMap<PathBuf, String>,
+    ) -> Result<()> {
+        if redirects.is_empty() {
+            return Ok(());
+        }
+
+        log::debug!("Emitting redirects");
+
+        for (original, new) in redirects {
+            log::debug!("Redirecting \"{}\" → \"{}\"", original.display(), new);
+            let filename = root.join(original);
+            self.emit_redirect(handlebars, &filename, new)?;
+        }
+
+        Ok(())
+    }
+
+    fn emit_redirect(
+        &self,
+        handlebars: &Handlebars<'_>,
+        original: &Path,
+        destination: &str,
+    ) -> Result<()> {
+        if let Some(parent) = original.parent() {
+            std::fs::create_dir_all(parent)?;
+        }
+
+        let ctx = json!({
+            "url": destination,
+        });
+        let f = File::create(original)?;
+        handlebars.render_to_write("redirect", &ctx, f)?;
+
+        Ok(())
+    }
 }
 
 // TODO(mattico): Remove some time after the 0.1.8 release
@@ -343,6 +383,10 @@ impl Renderer for HtmlHandlebars {
         debug!("Register the head handlebars template");
         handlebars.register_partial("head", String::from_utf8(theme.head.clone())?)?;
 
+        debug!("Register the redirect handlebars template");
+        handlebars
+            .register_template_string("redirect", String::from_utf8(theme.redirect.clone())?)?;
+
         debug!("Register the header handlebars template");
         handlebars.register_partial("header", String::from_utf8(theme.header.clone())?)?;
 
@@ -401,6 +445,8 @@ impl Renderer for HtmlHandlebars {
             }
         }
 
+        self.emit_redirects(&ctx.destination, &handlebars, &html_config.redirect)?;
+
         // Copy all remaining files, avoid a recursive copy from/to the book build dir
         utils::fs::copy_files_except_ext(&src_dir, &destination, true, Some(&build_dir), &["md"])?;
 
diff --git a/src/theme/mod.rs b/src/theme/mod.rs
index b8c496c3..38aa22e9 100644
--- a/src/theme/mod.rs
+++ b/src/theme/mod.rs
@@ -15,6 +15,7 @@ use crate::errors::*;
 
 pub static INDEX: &[u8] = include_bytes!("index.hbs");
 pub static HEAD: &[u8] = include_bytes!("head.hbs");
+pub static REDIRECT: &[u8] = include_bytes!("redirect.hbs");
 pub static HEADER: &[u8] = include_bytes!("header.hbs");
 pub static CHROME_CSS: &[u8] = include_bytes!("css/chrome.css");
 pub static GENERAL_CSS: &[u8] = include_bytes!("css/general.css");
@@ -46,6 +47,7 @@ pub static FONT_AWESOME_OTF: &[u8] = include_bytes!("FontAwesome/fonts/FontAweso
 pub struct Theme {
     pub index: Vec<u8>,
     pub head: Vec<u8>,
+    pub redirect: Vec<u8>,
     pub header: Vec<u8>,
     pub chrome_css: Vec<u8>,
     pub general_css: Vec<u8>,
@@ -77,6 +79,7 @@ impl Theme {
             let files = vec![
                 (theme_dir.join("index.hbs"), &mut theme.index),
                 (theme_dir.join("head.hbs"), &mut theme.head),
+                (theme_dir.join("redirect.hbs"), &mut theme.redirect),
                 (theme_dir.join("header.hbs"), &mut theme.header),
                 (theme_dir.join("book.js"), &mut theme.js),
                 (theme_dir.join("css/chrome.css"), &mut theme.chrome_css),
@@ -120,6 +123,7 @@ impl Default for Theme {
         Theme {
             index: INDEX.to_owned(),
             head: HEAD.to_owned(),
+            redirect: REDIRECT.to_owned(),
             header: HEADER.to_owned(),
             chrome_css: CHROME_CSS.to_owned(),
             general_css: GENERAL_CSS.to_owned(),
@@ -175,6 +179,7 @@ mod tests {
         let files = [
             "index.hbs",
             "head.hbs",
+            "redirect.hbs",
             "header.hbs",
             "favicon.png",
             "css/chrome.css",
@@ -203,6 +208,7 @@ mod tests {
         let empty = Theme {
             index: Vec::new(),
             head: Vec::new(),
+            redirect: Vec::new(),
             header: Vec::new(),
             chrome_css: Vec::new(),
             general_css: Vec::new(),
diff --git a/src/theme/redirect.hbs b/src/theme/redirect.hbs
new file mode 100644
index 00000000..9f49e6d0
--- /dev/null
+++ b/src/theme/redirect.hbs
@@ -0,0 +1,12 @@
+<!DOCTYPE html>
+<html lang="en">
+  <head>
+    <meta charset="utf-8">
+    <title>Redirecting...</title>
+    <meta http-equiv="refresh" content="0;URL='{{url}}'">
+    <meta rel="canonical" href="{{url}}">
+  </head>
+  <body>
+      <p>Redirecting to... <a href="{{url}}">{{url}}</a>.</p>
+  </body>
+</html>